This invention relates to the preparation of amino carboxylic acid salts, and more particularly, relates to a method for the preparation of amino carboxylic acid salts by the reaction of amino alcohols with an alkali metal hydroxide in the presence of a Raney copper catalyst.
Amino carboxylic acid salts are useful in various applications. The glycine salt, for example, can be neutralized to glycine, which is widely used as an additive in processed meat, beverages, and in other processed food stuffs. It is also used widely as a raw material for pharmaceuticals, agricultural chemicals and pesticides. Iminodiacetic acid salt can be neutralized to iminodiacetic acid, and is used in various applications such as a raw material for the preparation of agricultural chemicals and pharmaceuticals. Nitrilotriacetic acid salt can be converted into nitrilotriacetic acid which is useful as a detergent builder. Other amino carboxylic acids that can be prepared by the process of the present invention have useful applications.
U.S. Pat. No. 4,782,183 to Goto et al. discloses a method for the manufacture of amino carboxylic acid salts which comprises subjecting an amino alcohol to an alkali metal hydroxide in the presence of a Raney copper catalyst.
In a patent application published by WIPO as WO 92/06069 on Apr. 16, 1992, a process is disclosed for producing glycine, iminodiacetic acid and nitrilotriacetic acid salts by contacting monoethanolamine, diethanolamine or triethanolamine with an alkali metal hydroxide in the presence of a Raney copper catalyst, wherein at least some of the Raney copper catalyst has been rejuvenated by treating the catalyst under reflux conditions with formic acid (attorney docket No 39-21(3145)).
A journal article "Structure and Activity of Chromium-Promoted Raney Copper Catalyst for Carbon Monoxide Oxidation" by Laine et al., Applied Catalysis, 44 (1-2), pages 11-22, discloses that chromium-promoted Raney copper catalysts were prepared, and their activity for the oxidation of carbon monoxide was measured. The surface area of the Raney copper catalyst was directly related to the aluminum content in the precursor alloy and to a lesser extent to the presence of chromium. Bulk cuprous oxide and cupric oxide were detected by X-ray diffraction in the Raney copper catalyst. The presence of chromium inhibited the formation of cupric oxide but not of cuprous oxide. The activity decreased as chromium content increased.
U.S. Pat. No. 4,810,426 to Fields et al., discloses a process for the production of N-phosphonomethylglycine by oxidizing N-phosphonomethylethanolamine or the cyclic internal ester thereof with an excess of an aqueous alkali and a copper catalyst, and thereafter heating at a temperature between 200.degree. and 300.degree. C. Thereafter, the salt is neutralized with an acid to produce the desired N-phosphonomethylglycine.
Although satisfactory results are achieved by the processes of the prior art to convert an amino alcohol to a amino acid using a copper catalyst, or even a Raney copper catalyst, it has been found that upon repeated usage of the Raney copper catalyst, the catalyst tends to agglomerate, and the activity of the catalyst decreases. Now, it has been found, in accordance with the teachings of the present invention, that the activity of the Raney copper catalyst can be extended to a significant degree, permitting more economic utilization of the catalyst.